docs: add markdown formatting for completion in editor example

[thoda-dev]

🔗 Linked issue

Resolves #5713

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 👌 Enhancement (improving an existing functionality)

📚 Description

With the example in the current documentation for AI completion in the editor, after completion, the markdown formatting is not applied.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[Copilot]

Pull request overview

This PR enhances the AI completion feature in the editor documentation example by adding markdown parsing and formatting support. Previously, markdown syntax like **bold** would be inserted as plain text; now it's properly rendered as formatted content.

Key changes:

• Added markdown parsing logic to convert raw markdown text into TipTap nodes/marks during completion insertion
• Implemented throttled streaming updates to improve performance during AI completion
• Restructured completion state management to track inserted ranges and handle inline vs. block content appropriately

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
EditorUseCompletion.ts	Added markdown parsing functions, throttling mechanism, and rewrote streaming insertion logic to apply markdown formatting during AI completion
EditorCompletionExtension.ts	Modified suggestion acceptance to parse markdown content and increased debounce delay from 250ms to 2500ms

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[pkg-pr-new]

npm i https://pkg.pr.new/@nuxt/ui@5714

commit: af69b5a

[benjamincanac]

I think it would be easier for the sake of the example to update the prompt in completion.post.ts to prevent it from returning markdown 🤔

[thoda-dev]

Probably, but I also think many people could encounter this "problem" while using code from the example and could see it as a bug

[benjamincanac]

Closing in favor of 86b0fb1.